Recyclable sheet material and a container thereof

ABSTRACT

The present invention relates to a recyclable sheet material and a container formed of such recyclable sheet material. The recyclable sheet material comprises a paper board coated on at least one uncoated surface with at least one of a water barrier coating and a first surface coating. The water barrier coating provides a surface with a smoothness equal to or less than 500 ml/min. The first surface coating may comprise at least one mineral pigment and at least one polymeric binder and may provide a surface with a smoothness that is 100 ml/min or less. The first surface coating may further be coated with a water barrier coating.

The present invention relates to a recyclable, preferably repulpablesheet material as defined below and a container, preferably a cup, basedessentially on cellulosic material for water containing foodstuff formedof such recyclable sheet material comprising

-   -   1a) a paper board which is coated with a water barrier coating        on at least one of its uncoated surfaces having a smoothness of        equal or less than 500 ml/min according to Bendtsen ISO 8791-2        or    -   1b) a paper board which is coated on at least one of its        uncoated surfaces with a first surface coating based on at least        one mineral pigment and on at least one polymeric binder,        preferably with polar groups, and which on top of the first        surface coating having a smoothness of 100 ml/min or less        according to Bendtsen ISO 8791-2 is coated with a water barrier        coating,    -   wherein each of said water barrier coatings being based on at        least one polymer having a melting point of at least 120° C. is        applied in an amount of providing a COBB value of the water        barrier coated paper board of equal or less 8 g/m² per 600 sec        and a surface energy equal or greater 38 mJ/m² at 20° C. (test        liquid:water) and    -   2) optionally a sealable coating covering at least partially in        designated areas the water barrier coating, which sealable        coating is based on at least one polymer, preferably with polar        groups, having a melting point of at least 10° C. below the        melting point of the polymer component of the water barrier        coating.

So called fast food restaurants are a major and growing supplier ofnutrition. Predominantly, the logical concept of fast food restaurantsis based on the single use package. Single use means that after theconsumption of the food, the package of the food is discarded.

Since such packages may consist of both cellulosic material,predominantly in form of fibres, like paper, paper board or other moldedfibre items, or plastic materials like polyethylene, polypropylene orpolyethylenterephtalate or of a mixture of cellulosic material andplastic material, a waste management based on recycling the materialcould be difficult, even impossible.

Although it is known that the big advantage of single use package isthat the used package need not be taken back for cleaning and thus a lotof energy consumption, like for heating dishwater and/or drying of thecleaned single use packages, is avoided, besides maintaining high andreliable hygienic standards for public use, the main stream of singleuse packages is worldwide a big problem.

The problem is related to the nature of the waste stream of single usepackages. As already mentioned, this waste consists of a mixture ofplastic material and cellulosic material typically. In order to recyclethis waste, it is necessary to separate the different materials whichcould be recycled after separation from each other. However, the wastestream containing a mixture of these materials makes it often impossibleto separate and recycle the different materials economically.

Traditionally, in the manufacture of paper and paper board, paraffinwaxes and synthetic polymers as plastic material are used as moistureretardants, water repellents, oil repellents, stiffness strengthenersand release agents. Consequently, the waste of such paper and paperboard of which single use packages traditionally are made, is not onlydifficult, but often impossible to be repulped and recycled in standardpaper mill processes, because the polymers, in particular the waxesderived from petroleum, are not biodegradable in mill white waters(circulated process waters) and discharge effluents. Additionally, theresidue of the waxes that can't be removed from the pulp fibers duringthe repulping and recycling process can cause severe problems due tobuildups that occur on the screens and felts used during the process offorming and making the paper or paperboard sheet.

It is also known that such waxes resist biodegradation and compostingwhen disposed off in landfills and other waste disposal systems.Consequently, paper and paper board coated or impregnated withtraditional synthetic polymers and waxes are also difficult and oftenimpossible to repulp and recycle owing to their resistance to separatefrom the fibres in the standard repulping processes resulting insignificant fibre losses in efforts to repulp and thus recycle them.Moreover, such synthetic polymers are also not biodegradable andtherefore resist composting.

It is known that such impregnated paper and/or paper board can only berepulped by using specialized repulping machinery that separates thepulp fibres from the laminated films and/or impregnation which is farmore expensive in terms of operating costs and/or recycled pulp fibreyields. The action of separating the fibres from any impregnatingsynthetic and/or plastic material damages some fibres causing them to beselected out of the recycled pulp and to be lost for reuse. Additionallya separated plastic material waste carries some of the fibres out of therepulpate when its adherence to the fibres is not hindered by therepulping process. Likewise, not only synthetic material used as sheetsfor the manufacture of paper and paper board, but also coatings andimpregnating products made from synthetic materials like waxes, can berepulped for recycling only in specially configured repulping equipmentthat removes and separates the waxes. However, these more intensephysical and chemical requirements of these repulping processes coupledwith a loss of fibres that become trapped in the wax cause therecyclable, repulpable fibre levels to fall far below those of thestandard repulping processes. In addition, packages made from suchproducts are not biodegradable and must be separated and deposited inseparate landfill areas.

It is therefore an object of the present invention to provide arecyclable sheet material especially for a container formed thereof,preferably for single use, based on cellulosic material, preferably on apaper board, which can be repulped and recycled according to standardpaper mill processes although having a sufficient high water barrierwhich allows the production of containers of various kinds especiallyuseful for foodstuff containing water. In addition the residue of therepulped sheet material, if any, is also preferably biodegradable andcan be composted when disposed off in a landfill or otherwise disposesystems.

This object is solved by providing a recyclable and preferablyrepulpable sheet material comprising

-   -   1a) a paper board which is coated with a water barrier coating        on at least one of its uncoated surfaces having a smoothness of        equal or less than 500 ml/min according to Bendtsen ISO 8791-2        or    -   1b) a paper board which is coated on at least one of its        uncoated surfaces with a first surface coating based on 70-90        dried wt % of at least one mineral pigment and on 10-30 dried wt        % of at least one polymeric binder, preferably with polar        groups, and optionally 1-5 dried wt % of auxiliary agents, with        the provision that all components are adding up to 100 dried wt        %, and which on top of that first surface coating having a        smoothness of 100 ml/min or less according to Bendtsen, ISO        8791-2, is coated with a water barrier coating,    -   wherein each of said water barrier coatings being based on at        least one polymer having a melting point of at least 120° C. is        applied in an amount of providing a COBB value of the water        barrier coated paper board 1a), respectively 1b), of equal or        less 8 g/m² per 600 sec and a surface energy equal or greater 38        mJ/m² at 20° C. (test liquid:water) and    -   2) optionally, a sealable coating covering at least partially in        designated areas the water barrier coating, which sealable        coating is based on at least one polymer, preferably with polar        groups, having a melting point of at least 10° C. below the        melting point of the polymer component of the water barrier        coating.

In order to achieve the recyclability of the inventive sheet materialrespectively any container formed thereof according to standard papermill processes the barrier coating of the sheet material must notinterfere with these processes however must guarantee a sufficient highwater and optionally grease barrier especially for any water containingfoodstuff being provided in any container, especially any cup, producedfrom the inventive sheet material. Accordingly, none of the coatings ofthe paper board, respectively the containers, especially the cupsproduced thereof, contain or comprise any wax or wax component.

Additionally, this is also only achieved by using as barrier material inan amount as low as possible but sufficient high to provide thenecessary water barrier expressed in a COBB value of equal or less 8g/m² per 600 sec and having a surface energy equal or greater 38 mJ/m²at 20° C. for guaranteeing the repulpability respectively recyclabilityaccording to standard paper mill processes by allowing an easyseparation between the polymer component of the water barrier coatingand any fiber material of the paper board.

Moreover, this repulpability of the inventive sheet material is furtherimproved by the fact that the necessary water barrier is alreadyachieved with a barrier coating amounting only to 10 g/m² at maximumthereby preventing any fiber clouding during the repulping process. Thisamount decreases with increasing smoothness of the paper board surfaceto be coated with the water barrier coating at a given COBB value.

Thus, a smooth surface of the paper board being coated with the waterbarrier coating is a requirement for achieving the necessary waterbarrier with such a low amount of coating.

Accordingly the inventive recyclable sheet material comprises a paperboard as substrate sheet of which at least one of its uncoated surfaceshas a smoothness of equal or less than 500 ml/min according to BendtsenISO 8791-2. This smoothness allows achieving the necessary water barrierexpressed as a COBB value of the water barrier coated paper board ofequal or less 8 g/m² per 600 sec, preferably 1-5 g/m² per 600 sec.

Alternatively the paper board 1b)already coated on at least one of itsuncoated surfaces with a first surface coating based on at least onemineral pigment and at least one polymeric binder which coated surfacehas a smoothness of 100 ml/min or less according to Bendtsen IS08791-2,can be coated with an even less amount of a water barrier coating,namely with an amount of as low as 3-9 g/m², more preferably 4-6 g/m²,for achieving a COBB value of the water barrier coated paper board ofequal or less 8 g/m² per 600 sec, preferably 1-5 g/m² per 600 sec.

The inventive recyclable sheet material comprises as substratepreferably a paper board having a grammage of 170-300 g/m².

The paper board having a grammage of 170-300 g/m² can already have on atleast one of its uncoated surfaces a first surface coating being basedpreferably on a dried water based dispersion consisting of at least onemineral pigment and at least one polymeric binder which polymeric binderhas preferably polar groups, and optionally auxiliary agents forachieving a smoothness of 100 ml/min or less according to Bendtsen ISO8791-2 of the coated surface.

Preferably, this first surface coating of the paper board 1b) comprisesat least one mineral pigment and at least one polymeric binderpreferably with polar groups. The mineral pigment component is at leastone mineral pigment selected from the group comprising clay, talc,calcium carbonate, titanium dioxide, kaolin or mixtures thereof,preferably clay or kaolin, most preferably clay.

Preferably, the polymeric binder is at least one polymeric binderselected from the group comprising polyacrylates, acrylate copolymers,preferably acrylate/styrene copolymers, polyvinyl acetates,ethylene/vinyl acetate copolymers, styrene copolymers, preferablystyrene/butadiene copolymers or styrene/butylacrylate copolymers, andmixtures thereof, most preferably acrylate copolymers.

Preferably these polymers are polymers having polar groups, preferablycarboxylic groups, carboxylic ester groups, carboxylic amide groupsand/or OH groups.

The first surface coating provides a surface energy equal or greater 38mJ/ m² at 20° C. (test liquid:water). In order to achieve this surfaceenergy and to provide a smooth surface of the paper board 1b) the firstsurface coating is applied preferably as water based dispersion on atleast one uncoated surface of the paper board 1b).

Thereby, after drying a first coating based on 70-90, preferably 75-85,dried wt % of at least one mineral pigment and 10-30, preferably 15-25,dried wt % of at least one polymeric binder is achieved.

For a person skilled in the art it is obvious that a water baseddispersion used for this application may also contain the usualauxiliary agents like thickening agents, defoaming agents, dispersants,anti-block agents, anti-static agents and/or slipping agents. Theamounts of all components of such first the dried surface coating areadding up to 100 dried wt %.

According to the present invention, the same kind of water barriercoating can be applied to at least one uncoated surface of a paper board1a), respectively on top of the first coating of the paper board 1b).

Such water barrier coating is also applied preferably as a water baseddispersion based on at least one polymer preferably with polar groupslike carboxylic-, carboxylic ester-, carboxylic amide- and/or OH-groupsand optionally usual auxiliaries. Preferably the polymer component ofthe water based dispersion is at least one polymer selected from thegroup comprising acrylate polymers, acrylate copolymers, methacrylatepolymers, methacrylate copolymers, styrene copolymers, preferablystyrene/acrylate copolymers, ethylene/vinyl acetate copolymers andmixtures thereof.

Preferably, the polymer component of the water based dispersion is atleast one acrylate polymer, acrylate copolymer, methacrylate copolymeror a mixture of an acrylate polymer with a methacrylate polymer, mostpreferably an acrylate/styrene copolymer.

Preferably, the water barrier coating is providing a surface energy ofequal or greater 38 mJ/m², more preferably from 38 to 55 mJ/m² at 20° C.(test liquid:water).

Preferably, the water barrier coating is applied as a water baseddispersion of the polymer component and optionally at least oneauxiliary agent in an amount of 1-5 dried wt %. As auxiliary agentsdispersants, thickening agents, defoaming agents, cross linking agents,anti-block agents, anti-static agents and/or slipping agents can beused. Most preferably the barrier coating is based on 95-99 dried wt %of the polymer component and 1-5 dried wt % of at least one auxiliaryagent with the provision that all components are adding up to 100 driedwt %.

The polymer component of the water barrier coating should have a meltingpoint of at least 120° C. unless the barrier coating also serves assealable coating. In such case, if no sealable coating 2) is present andthe barrier coating also functions as sealable material, the polymercomponent should have a melting point of equal or less 150° C.preferably from 120 to 148° C.

In case the water barrier coating does not function as a sealablematerial the barrier coating is covered by a sealable coating at leastin designated areas. Preferably, the heat sealable coating is applied atleast partially in the areas which have to be joined for the formationof a container formed of the inventive recyclable sheet material.

The sealable coating is based on at least one polymer, preferably withpolar groups having a melting point of at least 10° C. below the meltingpoint of the polymer component of the water barrier coating. Preferably,the sealable coating is based on a polymer component having a meltingpoint of 120° C. or less.

Preferably, the sealable coating is based on at least one polymerselected from the group comprising acrylate polymers, acrylatecopolymers, methacrylate polymers, methacrylate copolymers, ethylenevinyl acetate copolymers, styrene copolymers, preferablystyrene/acrylate copolymers and mixtures thereof, most preferableacrylate/styrene copolymers.

Preferably, the polymer used for the sealable coating has polar groupslike carboxylic-, carboxylic ester-, carboxylic amide- and/or OH-groupsproviding a surface energy of equal or greater 38 mJ/m², more preferablyfrom 38 to 55 mJ/m² at 20° C. (test liquid:water).

Besides the polymer component the sealable coating can optionallycontain auxiliary agents like thickening agents, defoaming agents,dispersants, cross-linking agents, anti-block agents, anti-static agentsand/or slipping agents in an amount of 1-5 dried wt %, more preferablythe sealable coating is based on 95-99 dried wt % of the polymercomponent and 1-5 dried wt % of at least one auxiliary agent, with theprovision that all components are adding up to 100 dried wt %.

Preferably the sealable coating is applied on a barrier coating in anamount 12 g/m² at maximum, more preferably in an amount of 6-10 g/m². Ifappropriate for the formation of a container by using the inventiverecyclable sheet material this amount can be split, preferably equallybetween the two preferably overlapping areas that have to be combinedfor the formation of a container, preferably a cup.

The polymer component of the barrier coating as well as of the sealablecoating has preferably a glass transition temperature T_(g) of 10-30° C.(measured according to DSC).

The sealable coating can also be applied as a water based dispersionwhich is dried after the coating like the first coating of paper board1b), respectively each of the water barrier coatings of paper board 1a),respectively 1b).

Each of the coatings, namely the first surface coating, the waterbarrier coating and the sealable coating, can be applied according toknown processes, whereby each of the coatings is dried and preferablycooled before the next coating is applied. The application of thecoatings can be carried out continuously by using equipment alreadyknown in the art, in-line or off-line the paper board production.Off-line coating is preferred in order to have the possibility fornecessary variations of the coating compositions.

Moreover the recyclable sheet material can also be coated on both of theuncoated surfaces of the paper board with the same sequence of coatingsas is applied to the first uncoated or coated surface of the paperboard. This sequence of coatings can also be manufactured by knownprocesses, preferably by laminating and/or coating and/or extrusion ofthe respective coating. Each coating can be applied on the paper boardweb, uncoated or already coated by means of blade coating, roll coating,rod coating, curtain coating or spraying.

A further object of the present invention is a container, preferably acup, most preferably a cup for single use, which is formed of theinventive recyclable sheet material.

In order to form the inventive container, the heat sealable material ofthe recyclable sheet material, is preferably activated by heat,preferably by hot air, and combined by pressing. The surface of therecyclable sheet material which is at least partially coated with theheat sealing material is preferably the inner surface of the containerwall.

According to the present invention the term “recyclable” means that thewhole content of cellulosic material (paper board) of the inventivesheet material, respectively inventive container, preferably cup, isrecyclable which means repulpable and the contents of the non-cellulosicmaterial like any coatings are at least repulpable according to standardpaper mill processes with standard process conditions without relying onany specially configured repulping equipment.

The amount of non-cellulosic material of the inventive sheet material,respectively of an inventive container, preferably cup, formed of theinventive sheet material is at most 15 wt % of the whole sheet materialor container, preferably cup.

The non-cellulosic material of the inventive sheet material,respectively inventive container, preferably cup, built thereof which isat least repulpable according to the before described definition iswater-dispersible or water-soluble, therefore preferably it can not onlybe repulped but also at least partially be recycled according to thestandard paper manufacturing processes or be degraded biologicallyaccording to DIN EN 13432.

The COBB value is determined according to DIN EN 20535:1994.

The inventive containers, preferably cups, can be produced according toknown manufacturing processes.

The inventive containers, preferably cups, are especially useful forproviding hot or cold beverages, ice cream or other hot or cold liquidsrespectively food. The provision of hot or cold liquids, especiallyaqueous liquids or ice cream, is preferred.

Additionally, it is evident that the inventive sheet material can alsobe used to produce other containers, especially for single use, thancups and optionally corresponding lids. These products can be trays,packages for milk and juices, plates or folded cartons for frozenfoodstuff. All these kinds of containers are especially suitable forsingle use.

1. A recyclable sheet material comprising: a paper board having agrammage of 170-300 g/m², said paper board being coated on at least oneuncoated surface with at least one of: 1a) a water barrier coating toprovide said at least one surface with a smoothness equal to or lessthan 500_ml/min according to Bendtsen, ISO 8791-2 and 1b) a firstsurface coating based on 70-90 dried wt % of at least one mineralpigment and on 10-30 dried wt % of at least one polymeric binder,wherein said first surface coating has a smoothness of 100_ml/min orless according to Bendtsen, ISO 8791-2, is coated with a water barriercoating, wherein said water barrier coating is based on at least onepolymer component having a melting point of at least 120_° C. and isapplied in an amount up to 10 g/m² at maximum providing a COBB value ofthe water barrier coated paper board 1a) and coated paper board 1b)equal to or less than 8 g/m² per 600 sec and a surface energy equal toor greater than 38 mJ/m² at 20_° C. (test liquid:water), and wherein anamount of non-cellulosic material is at most 15 wt % of the sheetmaterial.
 2. A recyclable sheet material according to claim 1 furthercomprising a sealable coating covering at least partially in designatedareas of each of said water barrier coating, wherein said sealablecoating is based on at least one polymer having a melting point of atleast 10_° C. below the melting point of the polymer component of thewater barrier coating.
 3. A recyclable sheet material according to claim1, wherein the water barrier coating amounts up to 10 g/m² at maximum,which amount decreases with increasing smoothness of the paper boardsurface coated with the water barrier coating at a given COBB value. 4.A recyclable sheet material according to claim 1, wherein the firstsurface coating of the paper board 1b) is based on at least a mineralpigment selected from the group consisting of clay, talc, calciumcarbonate, titanium dioxide, kaolin and mixtures thereof, and apolymeric binder.
 5. A recyclable sheet material according to claim 1,wherein the polymeric binder of the first surface coating of the paperboard 1b) is based on at least one polymer selected from the groupconsisting of polyacrylates, acrylate copolymers, acrylate/styrenecopolymers, polyvinyl acetates, ethylene/vinyl acetate copolymers,styrene copolymers, styrene/butadiene copolymers, styrene/butylacrylatecopolymers, and mixtures thereof.
 6. A recyclable sheet materialaccording to claim 1, wherein the first surface coating of the paperboard 1b) is based on a dried water-based dispersion comprising 75-85dried wt % of at least one mineral pigment and 15-25 dried wt % of atleast one polymeric binder.
 7. A recyclable sheet material according toclaim 1, wherein the water barrier coating is based on at least onepolymer selected from the group consisting of acrylate polymers,acrylate copolymers, methacrylate polymers, methacrylate copolymers,styrene copolymers, styrene/butylacrylate copolymers, ethylene/vinylacetate copolymers and mixtures thereof, said water barrier coatinghaving a surface energy equal to or greater than 38 mJ/m² at 20_° C.(test liquid:water).
 8. A recyclable sheet material according to claim1, wherein the water barrier coating is based on 95-99 dried wt % of thepolymer component and 1_-5 dried wt % of auxiliary agents, based on thetotal weight of the water barrier coating when said water barriercoating is dried.
 9. A recyclable sheet material according to claim 1,wherein the water barrier coating provides a COBB value of 1-5 g/m² per600 seconds of the coated paper board 1a), and coated paper board 1b).10. A recyclable sheet material according to claim 2, wherein thesealable coating is based on at least one polymer selected from thegroup consisting of acrylate polymers, acrylate copolymers, methacrylatepolymers, methacrylate copolymers, styrene copolymers, styrene/acrylatecopolymers, ethylene/vinyl acetate copolymers and mixtures thereof. 11.A recyclable sheet material according to claim 2, wherein said sealablecoating is coated on the water barrier coating in an amount of 12 g/m²at maximum at the designated areas of the water barrier coating.
 12. Arecyclable sheet material according to claim 2, wherein the sealablecoating is based on 95-99 dried wt % of the polymer component and 1-5dried wt % of auxiliary agents.
 13. A recyclable sheet materialaccording to claim 1, wherein the polymer component of the water barriercoating and the sealable coating each have a glass transitiontemperature T_(g) of 10_° C.-30_° C. (measured according to DSC).
 14. Arecyclable sheet material according to claim 1, wherein the waterbarrier coating also functions as a sealable coating having a meltingpoint equal to or less than 150° C.
 15. A recyclable sheet materialaccording to claim 1, wherein a second surface of the paper board isprovided with the same sequence of coatings as a first surface of thepaper board 1a), and paper board 1b).
 16. A recyclable sheet materialaccording to claim 1, wherein the recyclable sheet material is formed asa container, and wherein the water barrier coated surface is arranged asan inwardly directed surface of the container.
 17. A recyclable sheetmaterial according to claim 16, wherein the container is adapted forcontaining at least one of a hot beverage, a cold beverage, ice cream, ahot liquid, a cold liquid, a hot food and a cold food.
 18. A recyclablesheet material according to claim 16, wherein the container is adaptedfor single use.